C-driver for an 8 digit 7 segment display

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A multiplexer has been developed for use with an 8 digit 7 segment display.

Display modules are Kingbright CA56-12SYKWA or CA56-12SURKWA or similar.

Each is a 4 digit display with 4 outputs, one to activate each digit and 8 outputs one to activate each segment ('a' to 'g' plus the colon).

A multiplexer is required since without it every digit would display the same pattern.


The operation of the multiplexer is described in the .PDF attachment “Switch_matrix_operation”.

Circuit details are given in Eagle and .BMP fils “switch matrix circuit”.


The following four C modules are included:

To display integers from 0 to 99999999

To illuminate individual segments

To vary the display intensity

To drive digits singly in the absence of the multiplexer as an aide to fault finding on the pcb.


Note: Display of the colon/decimal point has not been implemented.


All C code is contained in the zip file “Driving the display”